Atmosphere

An atmosphere was a collection of gases that surrounded a celestial body that possessed sufficient mass, and therefore sufficient gravity to hold it. Examples included many planets, moons, and large asteroids. Almost all species in the galaxy needed some form of atmosphere to breathe.

As humans were the predominant species within the Galactic Republic, later the Galactic Empire, a large number of planets within it possessed an atmosphere that supported human life, having a sufficient amount of oxygen.

Atmospheres habitable for oxygen-breathing species were referred to as "Type 1" atmospheres.[1] On worlds with a "Type II" atmosphere, breath masks were advised for longer exposures.[2]